Removable stem for raise bit

ABSTRACT

A raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating the earth formations surrounding the pilot hole includes a removable drive stem. The removability of the drive stem allows the raise bit to be transported through small drifts and extends the useful lifetime of the raise bit. The raise bit body includes a multiplicity of rolling cutters for contacting and disintegrating the earth formations surrounding the pilot hole. A central opening extends through said raise bit body. One end of the drive stem extends into the central opening. A pair of flats is located near the end of the drive stem. A retaining element is positioned in the flats and is bolted to the raise bit body.

United States Patent [19] Mitchell NOV. 18, 1975 REMOVABLE STEM FORRAISE BIT [75] Inventor: Howard Earl Mitchell, Duncanville,

Tex,

[73] Assignee: Dresser Industries, lnc., Dallas, Tex.

[22] Filed: Mar. 7, 1974 [21 Appl. No.: 449,179

Justman 175/53 Primary Examiner-Frank L. Abbott AssistantE.\'aminer'Richard E. Favreau Attorney, Agent, or Firm-Eddie E. ScottABSTRACT A raise bit for enlarging a pilot hole into a larger diameterhole by disintegrating the earth formations surrounding the pilot holeincludes a removable drive stem. The removability of the drive stemallows the raise bit to be transported through small drifts and extendsthe useful lifetime of the raise bit. The raise bit body includes amultiplicity of rolling cutters for contacting and disintegrating theearth formations surrounding the pilot hole. A central opening extendsthrough said raise bit body. One end of the drive stem extends into thecentral opening. A pair of flats is located near the end of the drivestem. A retaining element is positioned in the flats and is bolted tothe raise bit body.

5 Claims, 2 Drawing Figures U.S. Patent Nov. 18, 1975 3,920,089

REMOVABLE STEM FOR RAISE BIT BACKGROUND OF THE INVENTION This inventionrelates to the art of earth boring and more particularly to a raise bitfor enlarging a pilot hole into a larger diameter hole by disintegratingthe earth formations surrounding the pilot hole.

A relatively large diameter hole may be provided between a firstlocation and a second location by an operation commonly referred to asraise drilling. The raise drilling operation begins by drilling a smalldiameter pilot hole through the earth from a first location to anopening at a second location using a small diameter pilot bit. After thepilothole is completed, the pilot bit is removed from the drill columnand a larger diameter raise bit attached. The raise bit is rotated anddrawn along the pilot hole thereby enlarging the pilot hole to thedesired size. I

On many occasions, the small diameter pilot hole extends to an areaaccessible only through a small drift or passage. The removable drivestem of the present invention provides the raise bit with a low profilethereby allowing the raise bit to be transported through low drifts orpassages. For example, a 72-inch diameter raise bit may be transportedthrough a drift having a 30-inch height whereas a 72-inch diameter raisebit without the removable stern requires a drift with at least a 52-inchheight.

During the raise drilling operation, a tremendous amount of wear andstress is imposed upon the raise bit. Generally, the pilot hole tends towander which results in a series of curves over the length of the pilothole. As the raise bit is drawn along the pilot hole, the drillinggeometry changes. This results in a tremendous amount of stress beingtransmitted to the raise bit when it is being drawn through the curves.The outside radius of the raise bit may be many times greater than theradius of the pilot hole; therefore, the moment developed is great. Whenresistance is encountered by cutters located on the outer radius of theraise bit as when drilling along a curve, it causes increased stress onthe raise bit. It can be appreciated that changes in formationsencountered during the raise drilling operation complicates theabove-mentioned conditions and adds to the drilling difficulties.

The tremendous stress and wear encountered during the raise drillingoperation causes some elements of the raise bit to wear out much earlierthan others, notably the cutters and the drive stem. The bit of thepresent invention allows the elements that have a relatively shortlifetime to be replaced thereby extending the lifetime of the bit andreducing cost. The drive stem is removable and, therefore, replaceableas are the individual cutters. This allows the elements that receive thegreatest stress and wear to be readily replaced. The relatively shortlifetime of the individual cutters results from their nearly constantcontact with the formations and the consequent exposure to wear andabuse. The drive stem also contacts the formations and receives a greatdeal of wear and abuse. The drive stem absorbs a large amount of stresssince it is the single link between the drill column and the body of thebit. All energy from the rotary equipment is transmitted to the bitthrough the drive stem.

The drive stem is often subject to failure prior to failure of the bodyof the raise bit. It is, therefore, desirable to be able to easily andquickly remove the stem from the raise bit and replace it with a newstem. The stem is generally constructed of a high-strength heat-treatedmaterial and would be weakened by welding. It is, therefore, desirableto be able to attach and remove the stem from the raise bit body withoutwelding. From the foregoing, it will be appreciated that the stem mustbe constructedof material that will stand up under the harsh conditionsencountered. Such material is expensive and any reduction in the amountof this material used is cost savings. The bit of the present inventionallows the stem to be manufactured from high-strength material, whereasthe body may include lower strength and, therefore, less expensivematerials.

The stem or a stabilizer section on the stem should be nearly the sizeof the pilot hole to insure a smooth raise drilling operation. In orderto use the same bit body in pilot holes of different sizes, it isdesirable to be able to remove the stem from the raise bit body andreplace it with an appropriately sized stem. The stem should be easy toremove and replace using simple hand tools. This allows the stem to bereplaced in the field under adverse conditions.

DESCRIPTION OF PRIOR ART A general description of a raised drillingoperation is presented in US. Pat. No. 3,220,494 to R. E. Cannon et al,patented Nov. 30, 1965. In the system disclosed in this patent, a pilothole is enlarged to the desired raise hole size by rotating and drawinga large diameter raise bit upward along the pilot hole.

In US. Pat. No. 3,659,659 to Carl L. Lichte, patented May 2, 1972, alarge diameter raise bit with a replaceable stem is shown. The body ofthe bit includes a multiplicity of cutting stages around a central axis.The raise bit is attached to the drill column by a replaceable stemconnected to the main body of the bit and the body of the bit includes aseries of plates separated by a series of hollow support elements.

Raise bits manufactured by The Robbins Company,

650 South Orcas Street, Seattle, Wash. 98108 include a SUMMARY OF THEINVENTION The present invention provides a raise bit for enlarging apilot hole into a larger diameter hole by disintegrating the earthformations surrounding the pilot hole. The body of the raise bitincludes a multiplicity of rolling cutters for contacting anddisintegrating the earth formations surrounding the pilot hole. Acentral opening extends through the raise bit body. One end of a drivestern extends into the central opening. At least one recess is locatednear the end of the drive stem. A retaining element is positioned in therecess and the retaining element is bolted to the raise bit body.

The drive stem of the raise bit of the present invention may be removedand a new drive stem inserted in its place. The retaining element isdisconnected from the raise bit body and removed from the recess on thestem. The stem may then be withdrawn from the central opening in theraise bit body. A new stem may be inserted in its place and theretaining element repositioned on the raise bit body, thereby lockingthe new stem to the raise bit body. The raise bit of the presentinvention may be transported through small drifts or passages byremoving the drive stem. The drive stem is reattached and the raise bitis ready for operation. The high-strength heat-treated stem is notweakened by welding. The raise bit body may be constructed of materialsthat are less expensive than the materials that make up the drive stem.Different sized drive stems may be attached to the raise bit body toallow the raise bit to be used in pilot holes of different sizes. Theremoval of the stem and replacement with a new stem may be accomplishedin the field under adverse conditions with simple hand tools. Zeroclearance is provided between the stem and the retaining element andbetween the retaining element and the raise bit body. This insures arigid connection between the drive stem and the raise bit body. Thedrive stem of the present invention may be easily removed and a new stemput in its place without removing the cutter saddles adjacent the stem.The above and other features and advantages of the present inventionwill become apparent from a consideration of the following detaileddescription of the invention when taken in conjunction with the drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded view of a bitconstructed in accordance with the present invention.

FIG. 2 shows a partial section of a portion of the bit shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, anexploded view of a raise bit constructed in accordance with the presentinvention is shown. The raise bit includes a raise bit body 11. Theraise bit body 11 consists of a cutter stage plate 19, having a centralopening 20. A multiplicity of saddles 22 are mounted on the cutter stageplate 19. A corresponding multiplicity of rolling cutters 21 arepositioned in the saddles 22. The rolling cutters 21 contact anddisintegrate the formations surrounding the pilot liole during the raisedrilling operation.

A drive stem is positioned in the central opening 20. A pair of flats 12and 13 has been machined into the lower shank 14 of the stem 10. Atwo-piece collar .23 clamps onto the flats 12 and 13. Sections 27 and 28of the two-piece collar 23 are connected and drawn together by bolts 31and 32 that extend through holes 33 and 34. Flange plates 24 and on thetwo-piece collar are bolted to flange plate 26 on the cutter stage plate19. The flange plate 26 is an integral part of the cutter stage plate19. Bolts 29 and extend into holes 39 in the flange plate 26 and securethe two-piece collar 23 and stem 10 to the raise bit body 11.

Referring now to FIG. 2, a view in a partial section of a portion of theraise bit of FIG. 1 is shown. The drive stem 10 is connected to thecutter stage plate 19 by the sections 27 and 28 of the two-piece collar23. The flange plates 24 and 25 are connected to the flange plate 26 bybolts 29 and 30. A multiplicity of dowel pins help prevent the stem 10from rotating in the raise bit body 11. The section 28 fits within theflat 12 on the drive stem 10. The shoulder 37 on section 28 is inabutment with the sholder 17 on drive stem 10. This prevents drive stem10 from being pulled through the central opening 20 in the flange plate19.

The structural details of a raise bit constructed in accordance with thepresent invention having been described, a raise drilling operation willnow be considered using the bit shown in FIGS. 1 and 2. The raisedrilling operation begins by drilling a small diameter pilot holethrough the earth from a first location to an opening at a secondlocation using a small diameter pilot bit. After the pilot hole iscompleted, the pilot bit is removed from the drill column and the raisebit shown in FIGS. 1 and 2 is attached to the drill column. The raisebit is rotated and drawn along the pilot hole thereby enlarging thepilot hole to the desired size. The two-piece collar 23 positioned inflats l2 and 13 on the drive stem 10 provides a rigid connection betweenthe drive stem 10 and the raise bit body 11.

The raise bit may be transported through small drifts or passages byremoving the drive stem 10 and transporting the drive stem 10 and raisebit body 11 through the small drift or passage separately. The bolts 29and 30 are removed, thereby disconnecting the flange plates 24 and 25from the flange plate 26. The bolts 31 and 32 are removed allowing thesections 27 and 28 of the two-piece collar to be removed from the flats12 and 13 in the drive stem 10. The drive stem 10 is withdrawn throughthe central opening 20 in the cutter stage plate 19 and the drive stem10 and raise bit body 11 are transported through the small drift orpassage. The drive stem 10 is inserted through the central opening 20 inthe cutter stage plate 19 and the sections 27 and 28 of the two-piececollar are positioned in the flats 12 and 13. The bolts 31 and 32 areinserted and the two-piece collar is locked to the drive stem 10. Bolts29 and 30 are inserted in the flange plates 24 and 25 and connected tothe flange plate 26. The drive stem '10 is again locked to the raise bitbody 11 and the raised bit is ready for operation.

Should the drive stem 10 experience failure prior to failure of theraise bit body 11, the drive stem may be removed from the raise bit body11 and a new drive stem inserted in its place. The bolts 29 and 30 areremoved, thereby disconnecting the flange plates 24 and 25 from theflange plate 26. The bolts 31 and 32 are removed allowing the sections27 and 28 of the two-piece collar 23 to be removed from the flats 12 and13 in the drive stem 10. The drive stem 10 may be withdrawn through thecentral opening 20 in the cutter stage plate 19. A new drive stem may beinserted in place of the drive stem 10. If the raise bit is to be usedin a pilot hole of a different size, the new drive stem may have theappropriate diameter for the new pilot hole. The new drive stem isinserted through the opening 20 in cutter stage plate 19 and thetwo-piece collar connected together by bolts 31 and 32. The flangeplates 24 and 25 are again connected to the flange plate 26 by bolts 29and 30 and the raise bit is ready for operation.

The embodiments of an invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A bit for enlarging a pilot hole into a larger diameter hole bydistintegrating earth formations surrounding the pilot hole, comprising:

a main bit body including a multiplicity of cutters for contacting anddisintegrating earth formations surrounding the pilot hole;

a central opening in said main bit body;

a drive stem positioned in said central opening with a portion of saiddrive stem extending beyond said central opening;

recess means on the portion of said drive stem extending beyond saidcentral opening that provide said portion with a non-circular crosssection;

a retaining element positioned in said recess means, said retainingelement being a two-piece collar adapted to be bolted to said main bitbody; and means for attaching said retaining element to said main bitbody.

2. A raise bit for enlarging a pilot hole into a larger diameter hole bydisintegrating earth formations surrounding the pilot hole, comprising:

a cutter stage plate;

a multiplicity of saddles mounted on said cutter stage plate; I

a multiplicity of rolling cutters positioned in said saddles;

a central opening in said cutter stage plate;

a drive stem positioned in said opening with a portion of said drivestem extending below said central opening; r

recess means on the portion of said drive stem extending below saidcentral opening that provide said portion with a non-circular crosssection;

retaining element means positioned in said recess means, said retainingelement means .being a twopiece collar adapted to be bolted to saidcutter stage plate; and

means for attaching said retaining element means to said cutter stageplate.

3. A bit for enlarging a pilot hole into a larger diame ter hole bydisintegrating earth formations surrounding the pilot hole, comprising:

a main bit body including a multiplicity of cutters for contacting anddisintegrating earth formations surrounding-the pilot hole;

a central opening in said main bit body;

a drive stem positioned in said central opening with a portion of saiddrive stem extending beyond said central opening;

at least one flat on the portion of said drive stem extending beyondsaid central opening;

a retaining element positioned in said at least one flat, said retainingelement having a flat portion that fits against said flat and aconnecting portion; and

means for attaching said connecting portion of said retaining element tosaid main bit body.

4. A raise bit for enlarging a pilot hole into a larger diameter hole bydisintegrating earth formations surrounding the pilot hole, comprising:

a cutter stage plate;

a multiplicity of saddles mounted on saidv cutter stage plate;

a multiplicity of rolling cutters positioned in said saddles; 1

a central opening in said cutter stage plate;

a drive stem positioned in said opening with a portion of said drivestem extending below said central opening;

a recess on the portion of said drive stem extending below said centralopening that provides the portion with a non-circular cross section;

a retaining element positioned in said recess, said re taining elementcomprising a multiplicity of sections that at least partially surroundsaid drive stern and prevent said drive stem from rotating in saidcentral opening and being drawn through said central opening; and

' means for attaching said retaining element to said cutter stage plate.

5. A raise bit for enlarging a pilot hole into a larger diameter hole bydisintegrating earth formations surrounding the pilot hole, comprising:

a cutter stage plate;

a multiplicity of saddles mounted on said cutter stage plate;

a multiplicity of rolling cutters positioned in said saddles;

a central opening in said cutter stage plate;

a flange plate on said cutter stage plate;

a drive stem positioned in said opening with a portion of said drivestem extending below said central opening;

recess means -on the portion of said drive stem extending below saidcentral opening that provide said portion with a non-circular crosssection; retaining element means positioned in said recess means; flangeplate means on said retaining element means; and means attaching saidflange plates together. I Y

1. A bit for enlarging a pilot hole into a larger diameter hole bydistintegrating earth formations surrounding the pilot hole, comprising:a main bit body including a multiplicity of cutters for contacting anddisintegrating earth formations surrounding the pilot hole; a centralopening in said main bit body; a drive stem positioned in said centralopening with a portion of said drive stem extending beyond said centralopening; recess means on the portion of said drive stem extending beyondsaid central opening that provide said portion with a noncircular crosssection; a retaining element positioned in said recess means, saidretaining element being a two-piece collar adapted to be bolted to saidmain bit body; and means for attaching said retaining element to saidmain bit body.
 2. A raise bit for enlarging a pilot hole into a largerdiameter hole by disintegrating earth formations surrounding the pilothole, comprising: a cutter stage plate; a multiplicity of saddlesmounted on said cutter stage plate; a multiplicity of rolling cutterspositioned in said saddles; a central opening in said cutter stageplate; a drive stem positioned in said opening with a portion of saiddrive stem extending below said central opening; recess means on theportion of said drive stem extending below said central opeNing thatprovide said portion with a non-circular cross section; retainingelement means positioned in said recess means, said retaining elementmeans being a two-piece collar adapted to be bolted to said cutter stageplate; and means for attaching said retaining element means to saidcutter stage plate.
 3. A bit for enlarging a pilot hole into a largerdiameter hole by disintegrating earth formations surrounding the pilothole, comprising: a main bit body including a multiplicity of cuttersfor contacting and disintegrating earth formations surrounding the pilothole; a central opening in said main bit body; a drive stem positionedin said central opening with a portion of said drive stem extendingbeyond said central opening; at least one flat on the portion of saiddrive stem extending beyond said central opening; a retaining elementpositioned in said at least one flat, said retaining element having aflat portion that fits against said flat and a connecting portion; andmeans for attaching said connecting portion of said retaining element tosaid main bit body.
 4. A raise bit for enlarging a pilot hole into alarger diameter hole by disintegrating earth formations surrounding thepilot hole, comprising: a cutter stage plate; a multiplicity of saddlesmounted on said cutter stage plate; a multiplicity of rolling cutterspositioned in said saddles; a central opening in said cutter stageplate; a drive stem positioned in said opening with a portion of saiddrive stem extending below said central opening; a recess on the portionof said drive stem extending below said central opening that providesthe portion with a non-circular cross section; a retaining elementpositioned in said recess, said retaining element comprising amultiplicity of sections that at least partially surround said drivestem and prevent said drive stem from rotating in said central openingand being drawn through said central opening; and means for attachingsaid retaining element to said cutter stage plate.
 5. A raise bit forenlarging a pilot hole into a larger diameter hole by disintegratingearth formations surrounding the pilot hole, comprising: a cutter stageplate; a multiplicity of saddles mounted on said cutter stage plate; amultiplicity of rolling cutters positioned in said saddles; a centralopening in said cutter stage plate; a flange plate on said cutter stageplate; a drive stem positioned in said opening with a portion of saiddrive stem extending below said central opening; recess means on theportion of said drive stem extending below said central opening thatprovide said portion with a non-circular cross section; retainingelement means positioned in said recess means; flange plate means onsaid retaining element means; and means attaching said flange platestogether.